1. Field of the Invention
The present invention is directed to an apparatus for storing energy and subsequently transferring it to a vacuum arc such as used for supplying plasma to a plasma centrifuge. The apparatus incorporates an electrical circuit including a pulse forming network which is matched to the vacuum arc thereby providing an energy storage and arc initiating apparatus which is reliable, energy efficient, simple and of a relatively small physical size.
2. Description of the Prior Art
In plasma centrifuges of the type used for mass separation such as that described in Hirshfield et al, "Plasma Centrifuge" Physical Review Letters, Volume 46, No. 1, Jan. 5, 1981, the vacuum arc is triggered by a short focused laser pulse. The laser produced plasma initiates the discharge of a high voltage capacitor bank and a vacuum arc is formed. The energy efficiency is, however, very low because most of the stored energy is dissipated as heat in a series ballast resistor. This low efficiency of energy transfer has proven to be a decided disadvantage in the use of such a technique. Furthermore, the arc current is not constant during the pulse and the use of a laser for arc initiation necessitates an expensive, complex and not very reliable apparatus.
Another technique considered in supplying current to the vacuum arc is the use of a pulse forming network such as a Guillemin five section network of unequal lumped elements. In a Guillemin network, the elements (capacitors and inductors) are designed in such a way that a quasi-rectangular current pulse of duration .tau. is delivered into an ohmic load Z. The rise and fall of the current are linear, the rise time and fall time each being about 8% of .tau.. If the total resistance R of the network is of the same order of magnitude as the load impedance or larger, the current pulse becomes severly distorted. This situation occurred in prior art devices where the Guillemin pulse forming network was discharged into the extremely low impedance of the vacuum arc which is typically 40-80 milliohms because the inductors of the network were not designed to have a resistance much lower than the arc impedance.